First results from the ATLAS experiment

Australian Institute of Physics Congress

By Vivien Lee

It took less than 19 days of smashing lead ions together at the Large Hadron Collider in Switzerland for physicists confirm a new state of matter, the Australian Institute of Physics Congress was told in Melbourne. What the huge particle detector attached to the collider, known as the ATLAS experiment, has found is the first direct evidence of the Quark-Gluon Plasma—a 200 million degree Celsius soup of subatomic particles.

“It’s the very definition of primordial,” said Dr Martin White, a postdoctoral fellow from the University of Melbourne who is working on the project.

When particles collide at extremely high energies, their constituents spray in all directions creating ‘jets’ of matter, some larger than others. The ATLAS discovery was made when one of two large jets went missing— lost in the plasma in a process called ‘jet quenching’. This direct evidence builds upon the early hints of the Quark Gluon Plasma first found at the RHIC collider in New York.

“It’s like trying to jab a shard of frozen syrup through a mass of boiling syrup. It just doesn’t come out the other side,” said White. This phenomenon was observed in the first few days of atomic collisions at the LHC.

“This is the first direct observation of jet quenching, an exciting discovery for ATLAS in heavy ion physics,” says White.

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Abstract summary:

The Large Hadron Collider at CERN, Geneva, is in its first year of searches for new theories of particle physics. I will review the first results from the ATLAS detector.


Martin White,